The 17-year-old boy who allegedly ran over and killed a father and the man's 9-year-old daughter riding their bicycles in Concord could be released as early as Tuesday evening as authorities decide whether he should be charged, police said Monday.

Juvenile suspects must be released if charges aren't filed within two business days of an arrest. It may take police two to three weeks to investigate Saturday's crash, Concord police Lt. Bill Roche said Monday.

Among the questions authorities want answered is whether the teenager was texting or talking on a cell phone when he allegedly drove his sport utility vehicle into Solaiman Nuri, 41, and his daughter Hadessa as the two rode their bikes on the sidewalk on Treat Boulevard.

The boy, a student at Olympic Continuation High School in Concord, was booked Saturday on suspicion of vehicular manslaughter and is being held at Contra Costa County juvenile hall in Martinez. The Chronicle is not naming him because he is a minor and has not been charged as an adult.

Making decision

If a case is brought against him, he would probably be charged as a juvenile because vehicular manslaughter is normally not among the crimes for which prosecutors can directly bring a minor to adult court, said Dan Cabral, a senior deputy district attorney.

But prosecutors could still ask a juvenile-court judge to send the case to adult court, taking into consideration the severity of the crime, any criminal history and other factors.

Police said a preliminary investigation showed that the boy had been speeding and had made an unsafe lane change, possibly to get around another car, before the 9:30 a.m. crash.

But investigators need the results of toxicology tests and cell-phone records to determine whether the boy may have been under the influence or using his phone when he lost control of a 2002 Cadillac Escalade and drove onto the sidewalk, killing Nuri and his daughter, a third-grader at Woodside Elementary School in Concord.

'Hard evidence'

Witnesses told police the boy had been driving faster than the 45-mph speed limit, but no one has come forward to say they saw him using a phone, said police Capt. David Downing.

"So, ergo, we need the hard evidence," he said.

A friend of the teenage driver, Adam Gartside, said Saturday that the boy had called him after the crash and was "shocked and scared."

Hadessa's 12-year-old sister, Hannah, suffered minor injuries in the crash. She and her mother, Stoorai Nuri, a trauma nurse at John Muir Medical Center in Walnut Creek, attended a vigil for the victims at the crash site Sunday night.

Smoothies in holders

Solaiman Nuri and his daughters were riding on the sidewalk eastbound on Treat near Oak Grove with their helmets on when the westbound SUV careened onto the sidewalk, shearing off a fire hydrant before crashing into a building, police said.

Stoorai Nuri usually rode with her family but stayed home Saturday morning to cook breakfast for them, said her brother Emal Karzai, 26, of Dublin.

Her husband and children were riding from a nearby Jamba Juice, with their smoothies in their bikes' cup holders, when they were hit just a minute before they would have returned home, Karzai said.

Solaiman Nuri, known to friends as Sam, was an Afghan immigrant who doted on his family. He coached Hadessa's soccer team and drove a truck at the Port of Oakland, a job that allowed him to spend weekends with his wife and daughters, relatives said.

Once, Nuri attended a father-daughter dance after returning home from a long driving job and going more than 24 hours without sleep, Karzai said.

Faith in justice system

Karzai said the family is focusing its efforts on supporting Hannah and Stoorai Nuri rather than on how authorities will deal with the suspect.

"We have complete faith in the justice system," he said. "We know the facts are going to come out."

Karzai said of Stoorai Nuri, "This is just a roller coaster for her now. She has praised God for at least leaving her one daughter. It's a tragedy, but you have to look at the positive. She understands she has to be strong for her daughter, and her daughter has to be strong for her mother."